[PATCH] cpuset: hotplug documentation fix

[PATCH] cpuset: hotplug documentation fix

[Li Zefan]

If all the cpus/mems in a cpuset are offlined, the tasks in it will
be moved to the nearest ancestor with non-empty cpus/mems.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
---
 Documentation/cpusets.txt |   18 ++++++++++--------
 1 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/Documentation/cpusets.txt b/Documentation/cpusets.txt
index 1f5a924..871c1dd 100644
--- a/Documentation/cpusets.txt
+++ b/Documentation/cpusets.txt
@@ -635,14 +635,16 @@ prior 'mems' setting, will not be moved.
 
 There is an exception to the above.  If hotplug functionality is used
 to remove all the CPUs that are currently assigned to a cpuset,
-then the kernel will automatically update the cpus_allowed of all
-tasks attached to CPUs in that cpuset to allow all CPUs.  When memory
-hotplug functionality for removing Memory Nodes is available, a
-similar exception is expected to apply there as well.  In general,
-the kernel prefers to violate cpuset placement, over starving a task
-that has had all its allowed CPUs or Memory Nodes taken offline.  User
-code should reconfigure cpusets to only refer to online CPUs and Memory
-Nodes when using hotplug to add or remove such resources.
+then all the tasks in that cpuset will be moved to the nearest ancestor
+with non-empty cpus.  But the moving of some (or all) tasks might fail if
+cpuset is binded with another cgroup subsystem which has some restrictions
+on task attaching.  In this failing case, those tasks will stay
+in the original cpuset, and the kernel will automatically update
+their cpus_allowed to allow all online CPUs.  When memory hotplug
+functionality for removing Memory Nodes is available, a similar exception
+is expected to apply there as well.  In general, the kernel prefers to
+violate cpuset placement, over starving a task that has had all
+its allowed CPUs or Memory Nodes taken offline.
 
 There is a second exception to the above.  GFP_ATOMIC requests are
 kernel internal allocations that must be satisfied, immediately.
-- 
1.5.4.rc3

Re: [PATCH] cpuset: hotplug documentation fix

[Paul Jackson]

Thanks for updating this, Li Zefan.

I would suggest one minor wording fix.  The past tense of bind is bound.
(Don't you just love how regular the English language is ;)?

So, replace:
  +cpuset is binded with another cgroup subsystem which has some restrictions
with:
  +cpuset is bound with another cgroup subsystem which has some restrictions

Either way:

Acked-by: Paul Jackson <pj@sgi.com>

-- 
                  I won't rest till it's the best ...
                  Programmer, Linux Scalability
                  Paul Jackson <pj@sgi.com> 1.940.382.4214

Re: [PATCH] cpuset: hotplug documentation fix

[Li Zefan]

Paul Jackson wrote:
> Thanks for updating this, Li Zefan.
> 
> I would suggest one minor wording fix.  The past tense of bind is bound.
> (Don't you just love how regular the English language is ;)?
> 

wiki:

binded

   1. (nonstandard) Bound; simple past tense and past participle of bind.

google binded gave me 405,000 items. :)

I'll fix it and resend the patch

> So, replace:
>   +cpuset is binded with another cgroup subsystem which has some restrictions
> with:
>   +cpuset is bound with another cgroup subsystem which has some restrictions
> 
> Either way:
> 
> Acked-by: Paul Jackson <pj@sgi.com>
> 

Re: [PATCH] cpuset: hotplug documentation fix

[Paul Jackson]

> google binded gave me 405,000 items. :)

But "bound" gives me 135,000,000 items ;).

Thanks for putting up with me.

-- 
                  I won't rest till it's the best ...
                  Programmer, Linux Scalability
                  Paul Jackson <pj@sgi.com> 1.940.382.4214

[PATCH -v2] cpuset: hotplug documentation fix

[Li Zefan]

If all the cpus in a cpuset are offlined, the tasks in it will
be moved to the nearest ancestor with non-empty cpus.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Paul Jackson <pj@sgi.com>
---

fixed a typo: s/binded/bound

--
 Documentation/cpusets.txt |   18 ++++++++++--------
 1 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/Documentation/cpusets.txt b/Documentation/cpusets.txt
index 1f5a924..47e568a 100644
--- a/Documentation/cpusets.txt
+++ b/Documentation/cpusets.txt
@@ -635,14 +635,16 @@ prior 'mems' setting, will not be moved.
 
 There is an exception to the above.  If hotplug functionality is used
 to remove all the CPUs that are currently assigned to a cpuset,
-then the kernel will automatically update the cpus_allowed of all
-tasks attached to CPUs in that cpuset to allow all CPUs.  When memory
-hotplug functionality for removing Memory Nodes is available, a
-similar exception is expected to apply there as well.  In general,
-the kernel prefers to violate cpuset placement, over starving a task
-that has had all its allowed CPUs or Memory Nodes taken offline.  User
-code should reconfigure cpusets to only refer to online CPUs and Memory
-Nodes when using hotplug to add or remove such resources.
+then all the tasks in that cpuset will be moved to the nearest ancestor
+with non-empty cpus.  But the moving of some (or all) tasks might fail if
+cpuset is bound with another cgroup subsystem which has some restrictions
+on task attaching.  In this failing case, those tasks will stay
+in the original cpuset, and the kernel will automatically update
+their cpus_allowed to allow all online CPUs.  When memory hotplug
+functionality for removing Memory Nodes is available, a similar exception
+is expected to apply there as well.  In general, the kernel prefers to
+violate cpuset placement, over starving a task that has had all
+its allowed CPUs or Memory Nodes taken offline.
 
 There is a second exception to the above.  GFP_ATOMIC requests are
 kernel internal allocations that must be satisfied, immediately.
-- 
1.5.4.rc3